The present invention relates to an isolated output circuit that is suitable for low power applications.
Process control devices, such as rate/totalizer meters, frequently provide an isolated output that provides an indication that a certain count has been reached or an isolated output indicative of an alarm condition. A common circuit that is used to achieve an isolated pulse output employs an optical-coupler with an open collector interface. When the output is active, the open collector is pulled low for the period in which the output is on. As a result the open collector output draws current during the entire period that the open collector output is in the on state. Output circuits of this configuration are thus not well suited for battery powered applications.
It would therefore be desirable to have an isolated output circuit that is particularly suited for battery or other applications requiring low power consumption.